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Lamont-Doherty Earth Observatory Insert

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Lamont-Doherty Earth Observatory Insert ARCTIC Arctic Research Consortium of the United States Member Institution Spring/Autumn 1999 Arctic Research at Lamont-Doherty Earth Observatory Early Years of Lamont Research in the High Arctic olumbia University’s Lamont- CDoherty Earth Observatory (LDEO) entered the arena of arctic research more than four decades ago, when the Alaskan Air Command established Drifting Station A (or Alpha) on a 3 m-thick ice floe at 83° N 165° W. Station A was a U.S. con- tribution to the International Geophysical Year in 1957. Lamont scientists under the general direction of Jack Oliver and field leader- ship of Ken Hunkins conducted a pro- gram of geophysical and oceanographic research at the station, while investigators from other institutions carried out pro- grams of upper atmosphere, meteorologi- Lamont researchers have reconstructed annual temperatures for the arctic zone (65–90°N) during the past 400 years cal, sea-ice, and biological research. The using tree-ring width data from 12 sites near circumpolar treeline and three sites at northern, elevational treeline. Ten Lamont program used many instruments or more trees were sampled at each site. At all the sites, annual growth is limited by temperature. The regression used and techniques that had been developed principal component analysis to reduce the number of predictors and one forward lag of the series to account for carryover effects of temperature on tree growth. The regression explains 66% of the variance in temperature after adjustment for by Doc Ewing and other Lamont scientists degrees of freedom lost due to the regression. The tree-ring reconstruction helps quantify the unusual warming that is for exploration of the open oceans, modi- reflected in other arctic investigations. This and similar reconstructions provide a long-term context for interpreting fied for use from the ice camp. Important present changes in arctic regions (figure by Gordon Jacoby). results included the following: • echo soundings mapped the Alpha Rise • the first seismic refraction lines in the • a new understanding of wind-driven and Canada Abyssal Plain; Arctic Ocean led to understanding of motion of the ice pack was obtained. • measurements of currents yielded the upper crustal structure in the region; Other ice camps, most led by Ken the first direct observations of the • the first bottom photographs ever taken Hunkins, followed: Ekman spiral, which had been predicted in this ocean showed the life and ice- • Drifting Station Charlie led by George 50 years earlier; rafted rocks on the ocean floor; and Cvijanovich; • Fletchers Ice Island (T-3) from 1962– amont-Doherty Earth Observatory conducts a wide range of research in the 1974; LArctic and high-latitude regions of the northern hemisphere. These studies began • the Arctic Ice Dynamics Joint Experi- in 1957 with support from the U.S. Air Force Cambridge Research Center and, ment (AIDJEX) ice camps in the 1970s; soon thereafter, the Office of Naval Research (ONR). Support for recent and current • the Fram Expeditions in 1979. research is provided by ONR, the National Aeronautics and Space Administration The first Arctic Ocean precision depth (NASA), the National Oceanic and Atmospheric Administration (NOAA), the recorder and nuclear magnetic resonance Department of Energy (DOE), National Geographic, Palisades Geophysical Institute, magnetometer measurements were made the Geological Survey of Canada, and the NSF Office of Polar Programs, Ocean from Drifting Station Charlie. New Sciences program, Climate Dynamics program, and Earth System History program. instruments, such as the first satellite (continued on next page) 1 navigator—which was a classified system Research on Kodiak Island led to the Oceanic Uptake of Carbon Dioxide (CO2) at the time—and a seismic sparker, led to discovery of the “Fern Gap”, a Younger Since 1983, Lamont’s Ocean CO2 extensive mapping of Arctic Ocean Dryas equivalent, pointing to the dramatic Group, headed by Taro Takahashi, has bathymetry and sediment layers from T-3. role of this abrupt climate change in the been collaborating with Jon Olafsson Simultaneous profiling of temperature, North Pacific. (Marine Research Institute, Reykjavik, salinity, and currents at an array of four More recent research on the paleo- Iceland) for field studies aimed at under- AIDJEX camps revealed 127 separate sub- ecology of the Mesa Site, on the North standing seasonal and interannual changes surface anticyclonic eddies at depths of 50- Slope of Alaska, shows that peat formation in CO2 and nutrient chemistry and in 300 m. These eddies were approximately signals major environmental change in CO2 uptake in waters of the Irminger, 10 km in diameter and covered nearly the Arctic. Peteet, in collaboration with Iceland, and Norwegian seas. 25% of the Beaufort Sea. Helicopter sur- A. Andreev (Institute of Geography, In 1993–1995, researchers observed veys conducted from the Fram Expedition Moscow), has also led peatland research that the concentrations of CO2 and nutri- ice camps revealed anomalous diurnal tidal in Siberia and published results from the ents were drawn down by phytoplankton currents over the Yermak Plateau. The ice- Pur-Taz region of western Siberia. In col- blooms in mid-April through July. Con- camp studies were followed by the Mar- laboration with GISS modelers Anthony centrations of silicate, nitrate, and phos- ginal Ice Zone Experiment in 1983–84 Del Genio and Ken Lo, Peteet is continu- phate in surface water dropped from high and the Cooperative East Arctic Research ing sensitivity tests of climatic forcing winter values to nearly zero. Total CO2 Expedition in 1988–89, which gave new based on the paleoenvironmental results concentration was also drawn down at the results on the behavior of oceanographic from the Arctic and sub-Arctic. end of blooms. As a result, the partial pres- exchange through Fram Strait. Ice cores contain detailed records of sure of CO2 (pCO2) in surface water also paleoclimate, including large and abrupt dropped from 3% under-saturation in Paleoclimate Studies—Tree Rings changes in atmospheric dust. Dust found winter to approximately 24% under-satu- Gordon Jacoby and Rosanne D’Arrigo in polar ice cores can vary in amount by ration at the height of blooms. of the Tree-Ring Laboratory at Lamont more than two orders of magnitude. Pierre Thus, the oceans near and north of have been collecting samples at northern Biscaye and Francis Grousset are investi- Iceland become strong CO2 sinks during treeline (70°30' N) for more than two gating the continental origins of the dust spring through summer months. The decades. In 1989, the first reconstructions as indicators of past atmospheric change. strong drawdown of surface water pCO2 of large-scale temperature were published. Their approach has been to measure is one of the major processes causing the Since then, Lamont scientists and others characteristics of the dust that may high-latitude North Atlantic and its adja- have incorporated these data in many identify source areas. The tracers are: cent seas to be a major sink of CO2 in the reconstructions of northern hemisphere • clay mineralogy, which is dependent on global oceans. To document interannual and arctic temperature history. Ongoing the climate; and changes, the field study is continuing in studies in Alaska and the Taimyr Penin- • Sr-, Nd-, and lead-isotope composition, collaboration with research groups in Ice- sula, Siberia are producing new data for which are related to the rock type and land and other Nordic countries. improved reconstructions and information geologic age of the rocks from which about climatic and ecological changes in the local sediments in the source area Heat Flux and Ice Studies the Arctic. The Siberian studies, coordi- were derived. With the Surface Heat Budget of the nated with Russian scientists, are produc- In collaboration with Danish colleague Arctic (SHEBA) project (see Witness, this ing millennial-length records by using Anders Svensson, Biscaye and Grousset issue), Lamont has continued its long living, relict, and subfossil samples from have applied this approach to dust from tradition of ice-camp work in the Arctic. the northernmost trees on the planet. the two ice cores retrieved from the Doug Martinson is a co-principal investi- Greenland summit (see Witness Spring gator in the upper ocean physical oceanog- Paleoecology 1997), which hold records of the past raphy component of SHEBA. Martinson, The Paleoecology Lab at LDEO has a 110,000 years. The deserts of Eastern Asia Miles McPhee (McPhee Research), Tim history of research on Quaternary climate are the source of the Summit dust. The Stanton (Naval Postgraduate School), and and vegetation history along the southern researchers propose that if the source area Jamie Morison (University of Washing- coastline of Alaska. Projects led by of the dust has not changed significantly ton) are investigating the detailed hydro- Dorothy Peteet, also at NASA’s Goddard in size or location despite severe changes graphic structure of the upper 150 m of Institute for Space Studies (GISS), have in global climate and dust flux, then varia- the Arctic Ocean and how it evolves sea- used high-resolution pollen, macrofossil, tions in the amount of dust found in the sonally from continuous CTD profiles. and radiocarbon dating of lake and peat- cores must be the result of changes in the Some of the early findings include: land sediments. Peteet has focused particu- intensity of winds in the source area. • unusually fresh surface water,
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